TOPIC: Load Balancing T1's

I have three routers. One, a 2621, has 4 T1 ports. The other two are 2524's with 2 T1 ports each. I have two Point-to-point (PTP) T1's from the 2621 to one 2524 through our ISP. I have two PTP T1's from the 2621 to the other 2524 through house cable that runs across our business park.

I have two questions:

1. What is the best way to set up load balancing to maximize bandwidth? I have heard of two ways to do this. By setting up "equal cost" routes and by using CEF. I am not familiar with CEF but I heard I can do per-packet and per-destination load balancing with CEF.

2. Can I use the same method of load balancing with each group of T1's? The first two links are going through our ISP and the other two are going through house cable where I control the entire path.

I should probably tackle the first question before even worrying about the second question but I thought I would throw it out there. We are moving a lot of data across these lines.

Once I do it but with e1s in serial interfaces, Try PPP MULTILINK.
Obviusly In my case there was two clear channels, I changed the encapsulation to PPP, and created a multilink interface, its a virtual interface where you attach a bundle of physical interfaces where the frames are fragmented and balanced over the physical interfaces associated to the logical (multilink) interface.

try searching for multilink.

luck.

Its the same concept in ethernet like ether channel, but with serial interfaces.

As Havohej notes, PPP multilink is a way to achieve your load balancing. I've done a bit of digging myself and came across a very interesting article at Cisco, check it out and let us know what you think.

It seems like you can also use CEF (Cisco Express Forwarding) to get the same result, but this depends on the equipment and IOS version you've got.

Thanks for the responses. I'll look into it and get back. I'm getting the actual punch downs in place on Christmas and will begin testing the day after (since everybody will be home with their families).

Our 2621 is using IOS 12.2(12a) and our 2524's are both on 12.0(21). I guess I'm limited by the 2524's IOS but from the looks of it, I should be able to do what I'm looking for with 12.0(21).

That article is great. I especially appreciate the tables that lay out the pros and cons of each method. It looks like Multilink PPP is the way to go for both CPU utilizating and load balancing efficiency.

the only thing I can add is that troubleshooting with Multilink can be difficult. If one of the T1's should start experiencing errors or go down, I don't believe you can test a specific circuit without taking them out of the multilink configuration one by one.